Molecular basis of neurocognitive dysfunction and psychosis in Alpha-Mannosidosis

A significant portion of patients who are afflicted with lysosomal storage diseases (LSDs) encounter neurological manifestations, including cognitive issues and developmental delay, seizures, psychiatric issues, and an overall neurodegenerative decline. In order to enhance the development of effective therapies for these symptoms, it is imperative that we allude to the neuropathophysiology that underlies these manifestations. These distinct neurological and developmental features are particularly evident in patients with Alpha-Mannosidosis (AM), a type of LSD. However, there is limited published information regarding the mechanisms and pathophysiology of these presentations in patients with this condition. Although the precise impact of lysosomal storage on the biogenesis and functioning of neuronal cells has not been clearly defined, recent studies have placed emphasis on the significance of synaptic defects influencing this dysfunction. These defects encompass changes in synaptic spines, proteins, and vesicles, as well as postsynaptic densities that potentially precipitate functional disruptions in synaptic transmission and neurodegeneration. Ultimately, this cascade is thought to result in extensive neuronal loss and, consequently, the onset of cognitive manifestations. Uncovering the effects on synaptic components in LSDs with neurological symptoms like AM will enable a better understanding of disease progression. It will also allow us to identify critical targets for therapeutic intervention and the determination of optimal time frames for targeted treatments, as well as the effects of these treatments on mitochondrial function. The available therapeutic modalities in AM are not a definitive cure for affected patients, but rather an attempt to reduce the symptomatic severity in their presentation, while aiming to regress/slow down disease progression. This review will aim to discuss and rationalize the current treatment approaches in place for AM patients in relation to their effects on the improvement of neurocognitive symptoms in affected AM individuals.